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Wise et al.

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prevalence of AR in adults likely ranges between 10% and 41%, depending on the specific country.

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V.B. Incidence and prevalence of allergic rhinitis in children

There are relatively few studies on the incidence of AR in children. There is evidence that AR may start as early as during the first year of life. In the Cincinnati Childhood Allergen and Air Pollution Study (CCAAPS), 9% of the 12-month-old children with a parental history of respiratory allergy fulfilled the criteria of AR. 465 In the Pollution and Asthma Risk: an Infant Study (PARIS) birth cohort, 9.1% of the 18-month-old children had AR-like symptoms with a strong association with atopy and sensitization to inhalant allergens. Of these, 23.7% had rhinoconjunctivitis. 466 In a study of 29,662 children from the United States that used health care records to follow participants, the incidence of physician-diagnosed AR during the first year of life was 1%. From 1 to 5 years of age, the annual incidence was between 3.6% and 4.5%, with the highest incidence between 2 and 3 years of age. 467 This is broadly in line with estimates of a SAR incidence of 3% to 4% per year from 3 to 7 years of age reported in a birth cohort of 1314 German children. 468 In longitudinal studies, AR often occurs for the first time in childhood and increases in prevalence with increasing age. 467-471 Most children with symptoms of AR early in life have persistent symptoms for several years. 469-471 The International Study of Asthma and Allergies in Childhood (ISAAC) estimated the prevalence of allergic diseases in 2 different age groups, 6 to 7 years and 13 to 14 years, through a multicenter global survey. Two cross sectional surveys were performed approximately 7 years apart (range, 5 to 10 years). Overall, an increase in rhinoconjunctivitis prevalence was observed between the 2 surveys. 10 However, there were geographical differences in both baseline prevalence and in the increases observed; therefore, it is difficult to determine whether the observed differences represented a true increase in prevalence over time. The proportion of children with symptoms of rhinoconjunctivitis was higher in the older age group. Data from the second survey (ISAAC Phase Three 1999–2004) state that the worldwide prevalence of current rhinoconjunctivitis in the 6-year to 7-year-old age group was 8.3% (range between countries, 1.8% to 24.2%) and in the 13-year to 14-year age group was 15.1% (range, 4.5% to 45.1%). 472 In a more recent meta-analysis of all studies performed according to the ISAAC-protocol (1,430,329 children aged 0 to 18 years), the overall prevalence of AR was 12.66%. 473 Rhinoconjunctivitis has been reported to be slightly more common among boys than girls in the 6-year to 7-year-old age group, with the opposite tendency seen in the 13-year to 14 year-old age group. 474 However, gender differences were not seen in all countries in the survey. Other studies show a greater prevalence of AR among boys of all ages. For example, in the Isle of Wight (UK) birth cohort of 1456 children, the prevalence of rhinitis among boys as compared to girls was higher across all age groups (4 years 4.7% vs 2.1%, 10 years 14.9% vs 11.7%, 18 years 31.0% vs 24.0%). 469

V.C. Geographic variation of allergic rhinitis

The prevalence of AR shows marked geographic variation. Many factors likely contribute to this disparity and not all are completely understood. The central difficulty in meaningfully

Int Forum Allergy Rhinol . Author manuscript; available in PMC 2020 June 10.